The invention relates to a brake unit, particularly for providing manually controlled hydraulic braking action when the vehicle is being driven and automatic electric braking action when the operator leaves the vehicle.
Many vehicles, such as fork lifts, require both a manually actuated hydraulic brake while the vehicle is being driven and a security brake which operates automatically when the operator parks and leaves the vehicle. A variety of designs are used. In these designs, generally a switch will sense the departure of the driver from the seat and actuate a solenoid to cause a brake to lock. While workable, it is desired to have a more economical and less complex system.
A combination hydraulic and electrical parking brake is useful particularly for a forklift. The brake assembly mounts to a spindle or shaft that has a rotor that rotates with the shaft. The brake assembly has nonrotating coil, which when energized, attracts a plate to release the brake. When attracted to the coil, the plate compresses a set of coil springs. As long as electrical power is supplied to the coil, the electrical portion of the brake will not be operating. When electrical power ceases, such as when the driver leaves his seat, the coil springs cause the plate to push frictional pads against the rotor to prevent the rotor and shaft from turning. The brake assembly also has a piston. When hydraulic pressure is applied to the piston, it applies a frictional force to the rotor.